The Use of Frequency Compression by Cochlear Implant Recipients with Postoperative Acoustic Hearing

Background: The number of cochlear implant (Cl) recipients who have usable acoustic hearing in at least one ear is continuing to grow. Many such Cl users gain perceptual benefits from the simultaneous use of acoustic and electric hearing. In particular, it has been shown previously that use of an acoustic hearing aid (HA) with a Cl can often improve speech understanding in noise. Purpose: To determine whether the application of frequency compression in an HA would provide perceptual benefits to Cl recipients with usable acoustic hearing, either when used in combination with the Cl or when the HA was used by itself. Research Design: A repeated-measures experimental design was used to evaluate the effects on speech perception of using a Cl either alone or simultaneously with an HA that had frequency compression either enabled or disabled. Study Sample: Eight adult Cl recipients who were successful users of acoustic hearing aids in their nonimplanted ears participated as subjects. Intervention: The speech perception of each subject was assessed in seven conditions. These required each subject to listen with (1) their own HA alone; (2) the Phonak Naida HA with frequency compression (Sound Recover) enabled; (3) the Naida with Sound Recover disabled; (4) their Cl alone; (5) their Cl and their own HA; (6) their Cl and the Naida with Sound Recover enabled; and (7) their Cl and the Naida with Sound Recover disabled. Test sessions were scheduled over a period of about 10 wk. During part of that time, the subjects were asked to use the Phonak Naida HA with their Cls in place of their own HAs. Data Collection and Analysis: The speech perception tests included measures of coneonant identification from a closed set of 12 items presented in quiet, and measures of sentence understanding in babble noise. The speech materials were presented at an average level of 60 dB SPL from a loud-speaker. Results: Speech perception was better, on average, in all conditions that included use of the Cl in comparison with any condition in which only an HA was used. For example, consonant recognition improved by approximately 50 percentage points, on average, between the HA-alone listening conditions and the Cl-alone condition. There were no statistically significant score differences between conditions with SoundRecover enabled and disabled. There was a small but significant improvement in the average signal-to-noise ratio (SNR) required to understand 50% of the words in the sentences presented in noise when an HA was used simultaneously with the Cl. Conclusions: Although each of these Cl users readily accepted the Phonak Naida HA with SoundRecover frequency compression, no benefits related specifically to the use of SoundRecover were found in the particular tests of speech understanding applied in this study. The relatively high levels of perceptual performance attained by these subjects with use of a Cl by itself are consistent with the finding that the addition of an HA provided little further benefit. However, the use of an HA with the Cl did provide better performance than the Cl alone for understanding sentences in noise.